Process For Manufacturing Sound Absorbing Cement Tile

Abstract

A continuous process for manufacturing a sound absorbing tile made from a slurry including, quick setting cement, water, fibers and foaming agent, the process including the steps of (i) mixing cementitious material, water, foaming agent but without incorporation of prefabricated foam with fibers into a slurry; subsequently; (ii) injecting and distributing air into the slurry of step (i) to form a cellular slurry; subsequently; (iii) forming tiles or precursor products of tiles from the cellular slurry; and finally; (iv) allowing the cellular slurry to set into the desired tile or a precursor thereof.

Description

FIELD OF THE INVENTION [0001] The instant invention relates to a process for manufacturing acoustical cellular cementitious slurry. DESCRIPTION OF RELATED ART [0002] Cementitious materials are known for many years. Examples of cementitious material can be gypsum (which is available in many forms), Portland cement, sorrel cement, slag cement, fly ash cement, calcium alumina cement, and the like. [0003] U.S. Pat. No. 6,443,258 to Putt discloses a process for making sound absorbing panels in which plaster, fibers, water and foaming agent are mixed and simultaneously aerated using a mixing device similar to a kitchen aide mixer, orbiting and rotating mixing device. Air is entrapped, from the ambient, in the slurry, where the entrapment results from the combination of a dry mixture of plaster, (and optional additives) and of an aqueous mixture of water and surfactant. [0004] A typical industrial use is the manufacture of plaster wallboard. In this process air is usually introduced into t...

AI Technical Summary

Benefits of technology

[0024] The invention thus provides a continuous process for manufacturing a sound absorbing tile made from a slurry comprising, on a wet basis about 53 to about 68 wt % quick setting cement, about 17% to about 48 wt % water, about 0.05 to about 5 wt % fibers and about 0.01 to about 1 Owt % foaming agent, said tile having pores comprising interconnected voids and having a porosity from 75 to 95% by volume of said tile, said process comprising the steps of: (i) mixing cementitious material, water, foaming agent but without

Problems solved by technology

The mixer, which is usually a high shear mixer, assures the foam is completely combined with the plaster slurry but at the cost of a huge reduction in foam efficiency.

However, this additional water reduces the final strength of the gypsum matrix by unnecessarily increasing the space between the gypsum crystals and, thus, forming a weaker structure.

Further, these documents disclose processes that still provide the usual pore volume with no control over the size and distribution of the bubbles.

Air is entrapped, from the ambient, in the slurry, where the entrapment results from the combination of a dry mixture of plaster, (and optional additives) and of an aqueous mixture of water and surfactant However, the process used in this document is of the batch type, which rather unsuitable for an industrial use.

The type of mixer used in this document is not suited for the production of boards or panels on a conventional plasterboard line, since the slurry that is produced is of high viscosity so as to adhere to the wall, making this slurry completely unsuited for the production of boards or panels.

Last, this type of mixer presents the drawback of a lot of air loss.

This design presents the fatal flaw of being a pump of constant volume and with no control of share of air entering the pump.

Similarly, this device can entrain uncontrolled air carried into the mixer by the plaster.

The air, in this method, that is entrapped would be poorly mixed into the slurry, especially for quick-setting cement.

The mixer as described is not suitable for rapid setting cements because it permits long residence times due to the proportion of length to diameter and the vertical orientation.

Hence, this process relies on the addition of the foamer after the air bubbles have been created in the slurry, where the foamer introduced further adds water to the initial amount of water, and without control of the form of the bubbles in the hardened mass.

In the above documents to Mills and Mason, whenever a pump is used for entraining air, this does not result in favorable results since those pumps mentioned are not mixers and do not blend correctly.

None of the above documents discloses a process with specific air injection matured into a reliable, industrial process used for the manufacture of acoustical panels.

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